The majority of adult non-Hodgkin's malignant lymphomas and chronic lymphocytic leukemias are of B-cell origin. These patients often have hypogammaglobulinemia as well as negative skin test and abnormal T-cell mitogenic responses. We propose to study whether: 1) The malignant cells in untreated patients (obtained from involved tissues) have suppressor activity for immunoglobulin synthesis in vitro). 2) The supernatants of short-time cultures of these cells can exhibit suppressing or enhancing effects on Ig synthesis by normal lymphocytes. 3) The non-malignant mononuclear cells isolated from uninvolved peripheral blood and their supernatants have suppressor or enhancing effects on Ig synthesis when cocultured with lymphocytes from healthy donors. 4) The non-malignant lymphocytes from patients can be stimulated in vitro by Con-A to generate suppressor cells from DNA synthesis and Ig production in co-cultures of autologous and heterologous lymphocytes. The evaluation of suppressor or enhancing activity in co-cultures of normal and patient cells will be done by two methods: 1) Radioimmunoassay for the measurement of IgG, IgM and IgA by lymphocytes stimulated with PWM using a double-antibody radioimmunoassay. 2) Incorporation of H3-thymidine into DNA after stimulation by mitogens. This study may not only help in understanding the pathogenesis of lymphomas and leukemia but also may have both prognostic and therapeutic implications.